The present invention relates to day/night rearview mirror assemblies which have a high reflectivity day position and a reduced reflectivity night position, wherein reflection of undesired and distracting glare from behind a vehicle is reduced or eliminated in the night position, and more particularly, to an improved day/night rearview mirror assembly in which vibration of the mirror assembly is reduced.
Conventional day/night rearview mirrors employ a variety of systems to control movement between high and low reflectivity positions. Such assemblies normally include a toggle member or other actuator pivotally mounted in a rearview mirror case and a prismatic mirror element mounted to define a front face of the mirror assembly. In many prior known structures, a cam or overcenter type lever operator is used to pivot the case and prism with respect to the toggle. In turn, the toggle is commonly mounted on a ball joint or other mounting support which extends to a fixed member of a vehicle.
The toggle member may commonly be mounted to the case by a cylindrical shaft, supported in the case and extending through the toggle or by cylindrical stub shafts extending between the case and opposing sides of the toggle. The stub shafts may be fixed to the case with the toggle pivoting upon the stub shafts. Alternately, the stub shafts may be fixed to the toggle and pivot in supports formed in the case, or the stub shafts may be loose to pivot with respect to each of the toggle and the case. With any of these prior arrangements, the shaft means used is commonly cylindrical and offers no or little resistance to rotation of the toggle relative to the case.
Thus, in spite of whatever type of actuator is used to position the mirror assembly in the day or night positions, typically in an over center or toggle lever arrangement, some rotational movement between the toggle and the case will be allowed by the actuator. In addition, the wide spacing of the cylindrical or stub shafts on either side of the toggle can also lead to vibration. The combination of these actions will typically manifest as a relatively high frequency, low amplitude vibration of the mirror case and element, resulting in a blurred view through the mirror.
As a practical concern, the actuator must be relatively easily moveable between the day and night positions for convenient use of the mirror. However, the actuator may be made overly firm in an attempt to suppress vibration. In such a case, the actuator may so securely hold the mirror in one position, that a greater force is required to manipulate the actuator than is required to adjust the gross positioning of the mirror. This situation is quite likely to frustrate a user with the result that the day/night feature will not be used and the mirror will inappropriately be left in one position. This will in turn compromise a user's driving by reflecting glare at night or by reduced reflectivity during day.
Many prior known rearview mirror assemblies have also been unable to meet required standards for resistance to impact and bending as set by various countries or organizations such as the European Economic Community (EEC). Consequently, in order to enable use of a rearview mirror assembly on a world wide basis, it is necessary that a rearview mirror assembly meet or exceed such requirements for both impact and bending. The EEC standards provide that an assembly must resist breakage or scattering of broken glass when the mirror element is struck with a swinging pendulum having a rigid spherical weight of approximately 6.8 kilograms, for example. The assembly must also support a weight of 50 kilograms on its lower edge without breaking when supported horizontally with its rear support extending downwardly.
In addition to the above concerns, market pressures are present for reducing cost and minimizing component assembly weight as a part of continued emphasis on improved vehicle efficiency and economy.